The present invention relates to a heat exchanger in a simple structure which can be applied to a heat exchanger (EGR cooler) used in an exhaust gas recirculation apparatus in an automobile and other heat exchangers, in which a core body formed by turning up and bending a strip-shaped metal plate in a fanfold manner and having flat first flow passages and second flow passages alternately in the thickness direction of the metal plate, each of the first flow passages of the core body being blocked by each comb tooth of a pair of comb-state members at both end positions.
A conventional EGR cooler is made of an assembly of a large number of flat tubes or a large number of plates, a large number of fins, a casing and a header, in which cooling water is made to communicate through the casing side and an exhaust gas is made to communicate inside each of the flat tubes or the like as proposed in the invention described in Japanese Patent Application Laid-Open No. 5-18634.
Another heat exchanger in which a core of the heat exchanger is formed by a strip-shaped metal plate bent in a fanfold manner and a pair of comb-state members, the outer periphery being fitted with a cylindrical casing, and tanks are provided at both ends in the longitudinal direction as proposed in the invention described in WO 2004/065876 A1.
In the former heat exchanger such as the EGR cooler, the number of parts is large, which makes assembling cumbersome and increases the number of brazing portions on the parts, and there is a problem that a leakage tends to occur at the brazing portion.
In the core of the latter heat exchanger, comb teeth of the comb-state member are arranged at every other portion of the large number of flat groove portions in a core body formed in the fanfold state, and the groove bottom and the tip end of the comb tooth are bonded. And the casing is fitted with the outer periphery of the core. The casing is formed in the cylindrical state with a channel-state material covering three faces of the outer periphery of the core body and a lid member blocking the opening of the channel-state material, and the both ends are connected to the header. In this type of heat exchanger, there is a problem that a crack tends to occur at a joint between the casing and the core body, from which leakage of a fluid easily occurs. Along with that, leakage tends to occur at the brazing portion between the tooth base of the comb-teeth and the side face of the core body.
The present invention has an object to provide a reliable heat exchanger in which the number of parts is small, assembling is easy, strength at the brazing portion is high, and leakage is hard to occur.